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  1. WiredTiger
  2. WT-5968

Make the WT_SESSION_IMPL.txn field an allocated structure

    • Type: Icon: Technical Debt Technical Debt
    • Resolution: Fixed
    • Priority: Icon: Minor - P4 Minor - P4
    • WT10.0.0, 4.4.0-rc2, 4.7.0
    • Affects Version/s: None
    • Component/s: None
    • None
    • 5
    • Storage Engines 2020-04-06, Storage - Tora 2020-04-20

      Summary:

      Make the WT_SESSION_IMPL.txn field an allocated structure.


       

      We currently allocate a chunk of the WT_TXN structure when activating a WT_SESSION, the WT_TXN.snapshot field. Given the WT_TXN structure is itself relatively large (224B) and MongoDB allocates a large number of WT_SESSION structures (33K), we can save 7MB by allocating the entire WT_TXN structure on demand. Additionally, this reduces the size of the WT_SESSION_IMPL structure to 1K, likely a better size for allocation and alignment.

            Assignee:
            keith.bostic@mongodb.com Keith Bostic (Inactive)
            Reporter:
            keith.bostic@mongodb.com Keith Bostic (Inactive)
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              Created:
              Updated:
              Resolved: